Multiple foci of microinvasion is associated with an increased risk of invasive local recurrence in women with ductal carcinoma in situ treated with breast-conserving surgery
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The impact of Ductal Carcinoma in Situ (DCIS) with multiple foci of microinvasion (MI) (≤ 1 mm) on the risks of local recurrence (LR) and invasive LR is unknown, leading to uncertainty if DCIS with multiple foci of MI requires more aggressive treatment. We report a population-based analysis of the impact of multiple foci of MI, confirmed by pathology review, on the 15-year risks of LR and invasive LR treated with breast-conserving surgery (BCS) ± radiotherapy (RT).
Cohort includes all women diagnosed with DCIS ± MI from 1994 to 2003 treated with BCS ± RT. Cox proportional hazards model was used to evaluate the impact of multiple foci of MI on the risks of LR and invasive LR, adjusting for covariates. The 15-year local and invasive local recurrence-free survival rates were calculated using the Kaplan–Meier method with differences compared by log-rank test.
The cohort includes 2988 women treated by BCS; 2721 had pure DCIS (51% received RT), 267 had DCIS with one or more foci of MI (58% had RT). Median follow-up was 13 years. Median age at diagnosis was 58 years. On multivariable analyses, the presence of multiple foci of MI was associated with an increased risk of invasive LR (HR = 1.59, 95% CI 1.01–2.49, p = 0.04) but not DCIS LR (HR = 0.89, 95% CI 0.46, 1.76, p = 0.7). The 15-year invasive LRFS risks for cases with pure DCIS, with 1 focus or multiple foci of MI were 85.7%, 85.6%, 74.7% following treatment by BCS alone, 87.2%, 89.9%, and 77% for those treated with BCS + RT without boost and 89.2%, 91.3%, and 95% for women treated with BCS + RT and boost.
The presence of multiple foci of MI in DCIS is associated with higher 15-year risks of invasive LR after breast-conserving therapy compared to women with pure DCIS but treatment with whole breast and boost RT can mitigate this risk.
KeywordsDuctal carcinoma in situ DCIS Microinvasion Radiotherapy Local recurrence
The authors would like to acknowledge the following pathologists who contributed to the systematic pathology review: A. Tuck, B. Youngson, N. Miller, S. Done, M. Chang, S. Sengupta, P. Jani, L. Elavathil, M. Bonin and Dr. S. Robertson. This study was supported by the ICES, which is funded by an annual grant from the Ontario Ministry of Health and Long-Term Care (MOHLTC). The opinions, results, and conclusions reported in this paper are those of the authors and are independent from the funding sources. No endorsement by ICES or the Ontario MOHLTC is intended or should be inferred. This study was approved by the institutional review board at Sunnybrook Health Sciences Centre, Toronto, Canada. These datasets were linked using unique encoded identifiers and analyzed at the ICES. Parts of this material are based on data and information compiled and provided by Canadian Institute for Health Information (CIHI). However, the analyses, conclusions, opinions, and statements expressed herein are those of the author, and not necessarily those of CIHI. Parts of this material are based on data and information provided by Cancer Care Ontario (CCO). The opinions, results, view, and conclusions reported in this paper are those of the authors and do not necessarily reflect those of CCO. No endorsement by CCO is intended or should be inferred.
This work was supported in part by a grant from the Canadian Cancer Society Research Institute (grant number 18491). Dr. Rakovitch holds the LC Campbell Breast Cancer Research Chair.
Compliance with ethical standards
Conflict of interest
ERakovitch has received research grant funding from Genomic Health Inc. All other authors declare no conflict of interest.
This study was approved by the Sunnybrook Health Sciences Centre Research Ethics Board. It is an observational analysis, and no procedures or interventions were performed.
This is a population-based retrospective analysis. All personal identifiers for each case in this population cohort were removed. This study was facilitated through ICES which is named as a prescribed entity in Section 45 of PHIPA (Regulation 329/04, Section 18) which allows access and utilization of administrative data for research purposes with a waived requirement for consent.
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